Numerous documents, for example the article "Recent results in high-compression imaging coding" by M. Kunt, M. Benard and R. Leonardi, published in IEEE Transactions on Circuits and Systems, Vol. CAS-34, No. 11, November 1987, pp. 1306-1336, describe the coding technique based on pre-segmentation of each image into a set of regions while preserving the contours corresponding to the objects present within the image. Generally speaking, said segmentation consists of determining, in conformity with given criteria, regions within the image which are comparatively homogeneous, that is to say regions with a small or zero variation of the brightness, and of coding on the one hand the contents of these regions and on the other hand their contour.
Methods are now available which seem to be satisfactory for the coding, with data compression, of the texture or the contents of these regions. However, this does not hold for the contours which, since they are more numerous as the regions are more numerous, remain very expensive to code, because they represent a major part of the signals to be coded. Moreover, the signals thus coded contain a substantial redundancy because the contour of a region partly defines the contour of neighbouring regions.